The aim of the proposed research is to understand underlying mechanisms by which peptide hormones alter cell function. We will study the action of three hormones, thyrotropin-releasing hormone, insulin and epidermal growth factor, in promoting a common, acute metabolic response (increased nucleoside uptake) in an established, hormone-response, pituitary cell line (GH cells). Genetic and biochemical approaches will be utilized to study the nucleoside salvage pathway and its mode of regulation. The goal of these studies will be to identify factors involved in peptide hormone action which regulate the nucleoside salvage pathway. The role of cyclic AMP in hormonal control of nucleoside uptake will also be evaluated.